This invention relates generally to the field of motorized winding or reeling drums, usually referred to as winches, and more particularly relates to such winches that utilize DC motors as the power source. Even more particularly the invention relates to such winches wherein the DC motor is a brushless motor.
Powered winches for winding, spooling, retrieving or the like are well known devices, the winches commonly comprising a motor means rotating a shaft on which a drum or spool is mounted. For use where AC electrical power is not available, it is known to provide battery powered DC motors to drive the winch. DC powered motors may be classified as brush or brushless. In a brush motor, a spinning armature, the rotor, is mounted between permanent magnets, the stator. The armature contains an electromagnet which creates a magnetic field when electrical current is provided. The magnetic field attracts and repels the permanent magnets of the stator. In order to keep the rotor spinning, the poles of the electromagnet must be changed. This is accomplished by providing brushes which make contact with two spinning electrodes attached to the armature. Drawbacks to a brush DC motor are that the brushes wear out, sparking and electrical noise can result when the connections are made and broken, the brushes limit the maximum speed of the rotor, positioning the electromagnet in the center of the motor makes it harder to cool, and the number of poles available for the rotor are limited.
Because of these shortcomings, brushless DC motors have been developed that utilize relatively inexpensive computers and power transistors in place of the brush structure. In a brushless motor, the permanent magnets are mounted on the rotor and the electromagnets are positioned on the stator. In an in-runner brushless DC motor, the permanent magnets are mounted on a rotating shaft and the electromagnets are mounted in the housing. In an out-runner brushless DC motor, the permanent magnets are mounted on a rotating can or housing and the electromagnets are mounted on a fixed shaft. The rotor is kept spinning by alternating the polarity of the electromagnets. Advantages of a brushless motor include more precise speed control and more efficiency because of the computer control, there is no sparking and less electrical noise, there are no brushes to wear out, and the design allows for a large number of electromagnets on the stator.
Winches, especially portable winches, are often used in non-ideal conditions where dirt, debris, water or similar contaminants can cause damage to the motor. It is therefore an object of this invention to provide a winch powered by an out-runner brushless DC motor, wherein the motor is fully encased within the winch drum and wherein the shaft is fixed and the drum is mounted to the rotating housing. In this manner appropriate seals and bushings prevent ingress of contaminants into the motor.